"How does an Apple Watch owner know when its noon?"
"Their watch is dead"
That's what I'm thinking also. I've been actively testing WatchOS2 since the second beta and had severe battery issues in beta 3-5. My watch would die by 2:00pm every day. I finally uninstalled all third party apps and that fixed things. I tried to find the culprit by reinstalling the apps one at a time but was unable to find the little vampire.
I'm also having battery issues since the GM release. Beta 5 was fine, but now it doesn't even get through the morning.
Interesting, I'm on the GM and have better battery life than WatchOS 1.
Apparently un-pairing and pairing again fixes the issue, so will give this a try.